1. Field of the Invention
The present invention relates to a drill having a housing, a working spindle for receiving a tool and rotatably supported in the housing, and a hammer mechanism for generating axial blows to be imparted to the tool, with the hammer mechanism including a first cam disc connected with the working spindle for joint rotation therewith, a second cam disc supported in the housing without a possibility of rotation relative thereto but with a possibility of axial displacement therein, a spring located between a surface of the second cam disc facing in the direction opposite to the drilling direction and a surface in the housing facing in the drilling direction for biasing the second cam disc into the drilling direction, and an adjusting element for adjusting blow power of the axial blows imparted to the tool and displaceable parallel to the drilling direction.
2. Description of the Prior Art
For boring of stone, concrete and similar materials together with heavy boring and chisel tools also lighter and smaller boring, drilling and the like tool, which are equipped with a mechanical hammer mechanism that imparts blows to the tool only upon contact of the tool with a treated material under pressure, are used. Such a tool is disclosed in German Patent No. 1,427,725. The tool disclosed in the German Patent has a rotatable and axially displaceable working spindle and a cam hammer mechanism with cam discs slidable over each other. The working spindle is connected with an adjusting element for joint axial displacement therewith and is connected with a drive gear and one of the cam discs for joint rotation therewith. The other cam disc is fixedly secured in the tool housing. The adjusting element is formed as a sleeve-shaped member. It surrounds both cam discs and is displaced in the drilling direction by a spring.
The adjusting element cooperates with a control element which is located between the adjusting element and a surface in the housing facing in the drilling direction. The control element and the adjusting element have turned toward each other, end surfaces provided with corresponding spiral and ascending surfaces which, upon rotation of the adjusting element, slide over each other and determine, dependent on the degree of rotation of the adjusting element, the axial position of the working spindle defined by the axial position of the control surfaces. In this way, the blow power of the hammer mechanism is changed, or the cam elements of both cam disc are disengaged and no axial blows are imparted to the working spindle. The imparting of axial blows to the working tool via the working spindle results in an increased loss of the impact power and in an early wear of the working spindle and of the supports provided in the tool for supporting the working spindle.
Accordingly, the object of the present invention is to provide a boring tool or a drill in which the axial blows generated by the hammer mechanism are transmitted by the hammer mechanism directly to the working tool received in the spindle,and in which an increase of the blow power can be achieved simply and rapidly.